1. Field of the Invention
The present invention relates to a static chuck apparatus for attracting and securing a conductive material, such as a wafer, by the force of static electricity, a method for manufacturing the same, and an adhesive and an insulating film used for the manufacture thereof.
This application is based on Japanese Patent Applications Nos. Hei 9-23192 and Hei 9-23193, the contents of which are incorporated herein by reference.
2. Background Art
In the process of processing semiconductor wafers, a chuck apparatus is used for securing a semiconductor wafer at a prescribed position in a processing machine. As the chuck apparatus, there are mechanical apparatuses, vacuum type apparatuses, and static type apparatuses. The static type apparatuses have the advantage that they can attract uneven wafers, are easy to manipulate, and can be used in a vacuum.
During the processing of semiconductor wafers, since heat energy is generated on the semiconductor wafer, the semiconductor wafer locally expands and deforms unless the heat energy is dissipated adequately. Therefore, it is important that the heat generated during the processing be permitted to escape through the chuck apparatus to make the temperature distribution on the semiconductor wafer uniform.
An example of a conventional static chuck apparatuses is disclosed in Japanese Patent Application, Second Publication, No. Hei 5-87177. As is shown in FIG. 6, this apparatus has an adhesive layer 2a, an insulating film 4b, an adhesive layer 2b, an electrode layer 3b in the form of a metal sheet, an adhesive layer 2c, and an insulating film 4a layered successively on a metal substrate 1, and a wafer 5 is attracted on the insulating film 4a. In the metal substrate 1, temperature controlling spaces 6 for controlling temperature, for example, through constant-temperature water are formed.
However, in the static chuck apparatus shown in FIG. 6, since there are two insulating films, i.e., the insulating film 4a between the wafer 5 and the electrode layer 3b, and the insulating film 4b between the electrode layer 3b and the metal substrate 1, it is difficult for the heat of the semiconductor wafer 5 to escape to the metal substrate 1, and therefore there if inadequate temperature control of wafers.
Further, in the static chuck apparatus shown in FIG. 6, because there are portions where the metal sheet electrode layer 3b is present and portions where the metal sheet electrode layer 3b is absent, the wafer attraction surface became uneven due to the thickness of the electrode layer 3b, and gaps were formed between the wafer and the wafer-attraction surface at the resulting concavities, leading to a problem in that the heat conduction became locally worse. In particular, this phenomenon is conspicuous at the outer circumference of wafers.
On the other hand, FIG. 7 shows a static chuck apparatus disclosed in Japanese Patent Application, First Publication, No. Hei 8-148549. In this apparatus, a relatively thick insulating adhesive layer 2 is formed on a metal substrate 1, an electrode layer 3a, in the form of a deposited metal film or a plated film, is formed on the insulating adhesive layer 2, and an insulating film 4 is bonded onto the electrode layer 3a, and a semiconductor wafer 5 will be attracted to the insulating film 4.
In comparison to the apparatus shown in FIG. 6, in the apparatus shown in FIG. 7, the total thickness of the insulating film 4 the electrode layer 3a, and the adhesive layer 2 is small, and therefore the heat conduction is improved. However, to secure satisfactory insulating properties, it is necessary that the thickness of the adhesive layer 2 be at least 40 to 50 micrometers, and therefore the heat conductivity is still not satisfactory.
Furthermore, when the static chuck apparatuses shown in FIGS. 6 and 7 are used many times, the insulating films 4a and 4 having wafer-attraction surfaces are fatigued. All the parts above the metal substrates 1 must then be replaced. In that case, the number of required steps for replacing them is large, and particularly in the case wherein a thermosetting adhesive is used, it is necessary to remove the adhesive layers by washing, which have been made insoluble, and it is desired to simplify the steps.